Pegjam,
I always did use several prefilters inside my cone filter, but I was always very careful. What you run into is that you get a clogged prefilter with a gallon of extremely hot syrup inside and you have to pick it up and dump it into the next prefitler. I usually used something like several spring loaded clothes pins on the top to hold the prefilters together. What I usually tried to do was to loosen all the sides of the clogged prefilter and then pick up one side and kinda let the other side fall down inside as the liquid rose up on and it would spill over into the next prefilter.
This is dangerous and you have to be careful, but it works very good and I have never gotten burned other than just a minor burn or two. I used this method for several years and it worked good for my cone filtering tank. One thing to remember is that the clogged prefilter is extremely hot and the sugarsand inside of it also. I usually tried to grab the bottom of the prefitler with a clothes pin to hold it. I also would hang the clogged one up over another container and let it drip for a while to get out as much syrup as possible.